A number of examples of damping devices of this kind, generally being part of a motor vehicle transmission, are known from the existing art.
In an automobile transmission, a torsion damping device of this kind is associated with a clutch capable of selectively connecting the engine to the gearbox, such as a friction clutch or a hydrokinetic coupling apparatus having a locking clutch, in order to filter out vibrations due to engine irregularities.
This is because a combustion engine exhibits irregularities due to the succession of combustion events in the engine cylinders, said irregularities varying in particular depending on the number of cylinders.
The function of the damping means of a torsion damping device is consequently to filter the vibrations caused by the irregularities, and they act before the engine torque has been transmitted to the gearbox.
Vibrations penetrating into the gearbox would otherwise cause therein, during operation, particularly undesirable shocks, noises, or acoustic impacts.
This is one of the reasons why one or more damping means, capable of filtering vibrations at at least one determined frequency, are used.
In the sector of transmissions, research toward achieving increasingly effective filtration has resulted, for certain applications, in the addition of a pendulum oscillator to the damping devices conventionally utilized both in friction clutches and in motor-vehicle hydrokinetic coupling apparatuses.
A pendulum oscillator, also called a “pendulum,” has at least one mass or flyweight, generally several, that is arranged around the rotation axis of the engine shaft and is free to oscillate around a notional axis substantially parallel to the rotation axis of the engine shaft.
When the masses of a pendulum oscillator react to rotational inconsistencies, they oscillate in such a way that the center of gravity of each of said pendulum masses oscillates around an axis substantially parallel to the rotation axis of the engine shaft.
The radial position of the center of gravity of each pendulum mass with respect to the rotation axis of the engine shaft, as well as the distance of said center of gravity with respect to the notional oscillation axis, are established so that in response to centrifugal forces, the oscillation frequency of each of the pendulum masses is proportional to the rotation speed of the engine shaft; said multiple can assume, for example, a value close to the predominant harmonic order of the vibrations responsible for strong rotational inconsistencies in the vicinity of idle speed.